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Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Starting point (some bits missing):
Final config can be 8800uF @ 500V (1100J) or 4400uF @ 1000V (2200J) using 2200uF @ 500V PEH169 series caps. I also have a load of PEH200 series 3300uF @ 500v which give 1650J & 3300J respectively, but these will probably destroy my thyristors . All caps used are re-formed first in 50V stages up to the full 500V over a period of about 3 hours each.
Schematic: ]washer launcher V1.pdf[/file]
NOTE: When used at the Cambridge Teslathon 2010, a Marx Generator on the adjacent table caused enough interference to make the bank trigger unexpectedly. Be VERY careful when charging a bank like this - expect the unexpected! Do NOT operate it in the presence of large amounts of interference.
Fully safety interlocked with charging disconnect during firing & automatic discharging if power fails etc. Handles up to two paralleled bricks with GDT drive. The circuit I drew up didn't seem to be too complicated but there sure seem to be a lot of wires in there... Built on an old shelf with some rubber feet underneath. Small xfrmr is 12-0-12 for logic, lights & contactors; large xfrmr is a step-up from 230 -> 360VAC for charging and to isolate the HT side. Stripboard has the fire button trigger & timing for the contactors, GDT drive and interlock control.
I'm using 4AWG cables mainly as I cannot bend or crimp the 0/1 AWG cables I have - all these jumpers are from the salvage of the kit in the link above. To be honest, 4AWG is a complete bas*ard to work with too...
Mostly complete - testing in progress with 3 out of 8 caps (all 2200uF @ 500V 17 milliohm ESR, i.e. bank ESR of about 4 milliohms) running at only 120VDC (about 50J) whilst I check the currents etc. Logic & interlocking seems to work fine... except for small annoyance - when its turned off, it trips the thyristor one last time - annoying...
Meter reads 0-100V for actual 0-1000V Just testing one of the bricks with only 3 caps installed...
Launch pad (after being glued back together) - subsequently, the launch pad ripped itself apart - a new epoxy-potted one is needed. About 15 turns of 2.5mm diam Cu sandwiched between two 4mm acrylic discs. Choke is 2mH @ huge amps (wound with thick Cu strips, 4mmx6mm x-section)
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
teravolt wrote ...
are any of those parts decoys, looks like a giant variable dc power supply.
No decoys - Its actually not complex - there are a few bits missing from the photo - mostly Cu busbars and big heavy cables - they come from some stuff intercepted before the WEEE bin... Most caps are 2200Uf @ 500vdc but I have a large batch of 3300uF @ 500VDC as well... all are IEC 60384 defined "long life" types and unused...
There are several "bricks" of increasing sizes as I expect to detonate a few - they are thyristors and start at 1800A peak one cycle up to the biggest at 6700A. The small stripboard is just a few timers to get the contactor interlocking sequences right - the gate drive is missing from it in the photo - the bigger bricks need a hefty gate drive current.
There is a strong hint hidden in the photo (not that its isn't pretty obvious anyway).
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Oh jeez! With 624 joules at 800v i could make a disk disappear into the sky, and the inertia alone caused it to break if i had a piece of steel above it... And they are normal caps, not low ESR, with 12 gauge wire coil...
I would be scared of that bank, especially at 2200j! Be careful...!
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Arcstarter wrote ...
Oh jeez! With 624 joules at 800v i could make a disk disappear into the sky, and the inertia alone caused it to break if i had a piece of steel above it... And they are normal caps, not low ESR, with 12 gauge wire coil...
I would be scared of that bank, especially at 2200j! Be careful...!
Its also intended as a can-crusher... and general nasty bit of kit...
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Good luck on your capacitor bank! Hope it all works out for you =) I recently got 4KJ of capacitors, now total 8KJ. Guess I'll have to see how yours goes...
As for the charger, anything in mind? Maybe a simple variac + MOT?
Don't forget the safty discharge too...never know.
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